# std::vector<T,Allocator>::size

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< cpp‎ | container‎ | vector

size_type size() const; |  | (noexcept since C++11) (constexpr since C++20)

Returns the number of elements in the container, i.e. std::distance(begin(), end()).

### Parameters

(none)

### Return value

The number of elements in the container.

### Complexity

Constant.

### Example

The following code uses `size` to display the number of elements in a std::vector<int>:

Run this code

    #include <cassert>
    #include <vector>

    int main()
    {
        std::vector<int> nums;
        assert(nums.size() == 0);
        nums = {1, 2, 3, 4};
        assert(nums.size() == 4);
    }

### See also

capacity | returns the number of elements that can be held in currently allocated storage (public member function)
empty | checks whether the container is empty (public member function)
max_size | returns the maximum possible number of elements (public member function)
resize | changes the number of elements stored (public member function)
sizessize (C++17)(C++20) | returns the size of a container or array (function template)

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